A paint primer is a preparatory coating that is applied to a surface before painting. Its main purpose is to provide a stable base for the paint to adhere to, as well as to improve the overall appearance and durability of the painted surface. A primer can also help to seal and protect the surface from damage caused by moisture, stains, and other factors that can affect the adhesion and longevity of the paint.
There are different types of paint primers available, such as oil-based, water-based, and shellac-based primers. The type of primer you choose will depend on the type of surface you are painting and the type of paint you will be using.